﻿50 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  vol. 
  93 
  

  

  2% 
  to 
  2%, 
  greatest 
  depth 
  of 
  body 
  5 
  to 
  6, 
  length 
  of 
  disk 
  31/2, 
  all 
  in 
  stand- 
  

   ard 
  length 
  ; 
  length 
  of 
  disk 
  much 
  greater 
  than 
  distance 
  from 
  tip 
  of 
  snout 
  

   to 
  front 
  of 
  disk 
  ; 
  distance 
  from 
  dorsal 
  origin 
  to 
  midbase 
  of 
  caudal 
  fin 
  

   contained 
  1% 
  to 
  1% 
  times 
  in 
  snout 
  tip 
  to 
  dorsal 
  origin; 
  anal 
  origin 
  

   under 
  base 
  of 
  the 
  third 
  or 
  fourth 
  dorsal 
  fin 
  ray 
  ; 
  caudal 
  peduncle 
  short, 
  

   its 
  depth 
  about 
  equal 
  to 
  its 
  length 
  and 
  about 
  3 
  times 
  in 
  base 
  of 
  dorsal 
  

   fin; 
  dorsal 
  fin 
  rays 
  11 
  to 
  13, 
  anal 
  10 
  or 
  11, 
  pectoral 
  18 
  to 
  21 
  (usually 
  

   19 
  or 
  20) 
  {Infratridens, 
  new 
  genus) 
  (Gulf 
  of 
  California; 
  southern 
  

  

  California) 
  Infratridens 
  rhessodon 
  (Rosa 
  Smith) 
  

  

  4&. 
  Gill 
  membranes 
  joined 
  opposite 
  upper 
  edge 
  of 
  pectoral 
  fin 
  base 
  ; 
  incisorlike 
  

   teeth 
  of 
  both 
  jaws 
  with 
  trifid 
  tips, 
  except 
  middle 
  pair 
  or 
  two 
  sometimes 
  

   smooth-tipped 
  ; 
  teeth 
  in 
  both 
  jaws 
  in 
  a 
  single 
  row, 
  lateral 
  2 
  to 
  4 
  conical 
  

   and 
  last 
  1 
  or 
  2 
  sometimes 
  strong 
  canines 
  ; 
  outer 
  lower 
  base 
  of 
  pectoral 
  

   fin 
  with 
  fleshy 
  pad 
  poorly 
  developed 
  and 
  without 
  any 
  trace 
  of 
  a 
  free 
  

   margin 
  ; 
  pelvic 
  fins 
  joined 
  about 
  halfway 
  out 
  fourth 
  to 
  sixth 
  pectoral 
  

   fin 
  rays 
  and 
  not 
  near 
  base 
  ; 
  dermal 
  flap 
  in 
  axile 
  of 
  pectoral 
  fin 
  joins 
  oppo- 
  

   site 
  fourth 
  to 
  tenth 
  pectoral 
  fin 
  ray 
  ; 
  width 
  of 
  head 
  BV2 
  to 
  6, 
  length 
  of 
  

   head 
  2% 
  to 
  5, 
  greatest 
  depth 
  of 
  body 
  6 
  to 
  10 
  (except 
  in 
  eos), 
  length 
  of 
  

   disk 
  4 
  to 
  6 
  (except 
  in 
  eos), 
  all 
  in 
  standard 
  length; 
  opercular 
  spine 
  

   not 
  strongly 
  developed 
  and 
  not 
  reaching 
  to 
  rear 
  of 
  head 
  {Arhaciosa 
  

   Jordan 
  and 
  Evermann). 
  

   5a. 
  A 
  pair 
  of 
  black 
  spots 
  (more 
  or 
  less 
  ocellate) 
  on 
  back 
  behind 
  head 
  over 
  

   pectorals 
  usually 
  distinct, 
  each 
  spot 
  well 
  separated 
  ; 
  dorsal 
  surface 
  of 
  

   back 
  in 
  front 
  of 
  dorsal 
  origin 
  variously 
  barred 
  or 
  mottled 
  or 
  dark 
  

   spotted 
  but 
  without 
  3 
  hourglass-shaped 
  large 
  dark 
  blotches. 
  ( 
  Species 
  

   inhabiting 
  waters 
  of 
  the 
  Pacific 
  coast 
  and 
  offshore 
  islands.) 
  

   6a. 
  Distance 
  from 
  base 
  of 
  last 
  dorsal 
  ray 
  to 
  midcaudal 
  fin 
  base 
  con- 
  

   tained 
  l%o 
  to 
  1% 
  times 
  in 
  length 
  of 
  dorsal 
  fin 
  base; 
  least 
  depth 
  

   of 
  caudal 
  peduncle 
  about 
  1.0 
  to 
  1% 
  times 
  in 
  length 
  of 
  caudal 
  

   peduncle 
  (from 
  base 
  of 
  last 
  anal 
  ray 
  to 
  midcaudal 
  fin 
  base) 
  ; 
  inter- 
  

   orbital 
  space 
  longer 
  than 
  length 
  of 
  ^out 
  ; 
  dermal 
  flap 
  of 
  skin 
  

   in 
  axis 
  of 
  pectoral 
  fin 
  with 
  its 
  upper 
  edge 
  joined 
  to 
  pectoral 
  fin 
  

   base 
  opposite 
  fifth 
  to 
  eleventh 
  pectoral 
  ray; 
  dorsal 
  rays 
  10 
  or 
  11 
  

   (usually 
  10), 
  anal 
  rays 
  7 
  to 
  9 
  (usually 
  8 
  or 
  9) 
  ; 
  pectoral 
  fin 
  rays 
  

   19 
  or 
  20 
  ; 
  middle 
  teeth 
  of 
  both 
  jaws 
  with 
  trifid 
  tips, 
  middle 
  denticle 
  

   usually 
  longest 
  on 
  lateral 
  teeth, 
  worn 
  down 
  in 
  adults 
  (Gulf 
  

  

  of 
  California) 
  Arbaciosa 
  humeralis 
  (Gilbert) 
  

  

  6b. 
  Distance 
  from 
  base 
  of 
  last 
  dorsal 
  ray 
  to 
  midcaudal 
  fin 
  base 
  con- 
  

   tained 
  0.75 
  to 
  0.9 
  in 
  length 
  of 
  dorsal 
  fin 
  base 
  ; 
  least 
  depth 
  of 
  caudal 
  

   peduncle 
  1.6 
  to 
  2 
  times 
  in 
  length 
  of 
  caudal 
  peduncle. 
  

   7a. 
  Pectoral 
  fin 
  rays 
  22 
  to 
  24 
  (usually 
  23) 
  ; 
  dorsal 
  rays 
  usually 
  8 
  (7 
  

   to 
  9), 
  anal 
  7 
  or 
  8 
  (usually 
  8) 
  ; 
  greatest 
  width 
  of 
  head 
  contained 
  

   Sy2, 
  length 
  of 
  head 
  2% 
  to 
  2%, 
  in 
  standard 
  length 
  ; 
  snout 
  a 
  little 
  

   longer 
  than 
  width 
  of 
  interorbital 
  space; 
  middle 
  teeth 
  of 
  both 
  

   jaws 
  with 
  trifid 
  tips 
  (Mazatlan, 
  Mexico). 
  

  

  Arbaciosa 
  eos 
  (Jordan 
  and 
  Gilbert) 
  

  

  7b. 
  Pectoral 
  fin 
  rays 
  usually 
  19 
  to 
  21 
  (rarely 
  22). 
  

  

  8a. 
  Middle 
  incisorlike 
  teeth 
  of 
  both 
  jaws 
  (at 
  least 
  on 
  adults) 
  with 
  

  

  smooth 
  tips, 
  the 
  lateral 
  incisors 
  trifid 
  ; 
  pectoral 
  fin 
  rays 
  usually 
  

  

  about 
  21 
  ; 
  bony 
  ridges 
  on 
  snout 
  weakly 
  developed. 
  

  

  9a. 
  Dorsal 
  rays 
  8 
  to 
  10 
  (usually 
  9) 
  ; 
  anal 
  8 
  or 
  9 
  (usually 
  8) 
  

  

  (Peru) 
  Arbaciosa 
  pyrrhocincla 
  pyrrhocincla 
  (Cope) 
  

  

  9b. 
  Dorsal 
  rays 
  8 
  ; 
  anal 
  7 
  or 
  8 
  (Galapagos 
  Islands). 
  

  

  Arbaciosa 
  pyrrhocincla 
  truncata 
  Heller 
  and 
  Snodgrass 
  

  

  